JPS60208629A - Light deflector device - Google Patents

Abstract

PURPOSE:To improve the rotary precision of a polyhedron mirror by directly turning and driving the mirror which is floated by a magnetic bearing part and axially supporting said mirror by means of a dynamic pressure fluid bearing to make no contact with a fixed shaft which is engaged coaxially in said polyhedron mirror. CONSTITUTION:A light deflector consists of a polyhedron mirror 1, a magnetic bearing part 2 which floats the polyhedron mirror 1 and bears axial force, a dynamic pressure gas bearing part 3 which bears both an axial force and a radial force applied at right angles with the axial direction of the polyhedron mirror 1, and a rotary driving part 4 which turns the polyhedron mirror 1 at high speed. The dynamic pressure gas bearing part 3 consists of both a tapered through-hole 5 which is drilled coaxially in the central line part of the polyhedron mirror 1 and has a largest diameter at the uppermost end thereof, and a fixed shaft 7 which is suspended from an upper base body 6 and engaged in the through-hole 5 to make no contact therewith. In addition, the magnetic bearing part 2 consists of both a permanent magnet 9 annularly surrounding a mounting part 1a and another permanent magneto 10 which faces with said magnet 9 and is stuck to the upper base body 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical deflection device 5 that scans a laser beam by rotating a polygon mirror.

[Technical background of the invention and its problems]

Recently, optical deflection devices have been introduced as central mechanisms in MI and photo transfer type printers (laser printers) that print characters and symbols using laser light.

In such laser printers, it is necessary to rotate the polygon mirror that scans the laser beam at high speed in order to print at high speed. Therefore, generally, a rotating shaft on which a polygon mirror is supported is floated in a non-contact manner by a magnetic thrust bearing, and is supported by a pair of dynamic pressure gas journal bearings. and.

The rotating shaft is rotated by a rotor attached to the rotating shaft and a stator fixed to the rotating shaft. As a result, the overall size of the device has to be increased, which is an impediment to efforts to reduce the weight and size of the optical deflection device. Furthermore, since the above-mentioned polygon mirror requires high-speed rotation of several thousand rotations per minute, half frequency occurs due to the mismatch between the direction of axial displacement and the direction of the restoring force against that displacement. yv (HFW; Half Freq
rotation is likely to become unstable due to K. Therefore, it is necessary to strictly control the dimensional accuracy of the dynamic pressure gas journal bearing and the concentricity of both.

However, due to the fact that two or more types of bearings are incorporated, the shape is complex, and the number of parts is large, it is difficult to achieve the desired machining accuracy. Something.

It is an object of the present invention to provide an optical deflection device that has high rotational accuracy and is easy to manufacture.

[Summary of the invention]

The polyhedral part is directly suspended by the magnetic bearing part, the floating polyhedral part is directly rotationally driven, and the movement generated between the polyhedral part and the fixed shaft that is coaxially and non-contactly fitted into the polyhedral part is The polyhedral part is supported non-contact by pressure.

[Embodiments of the invention]

An embodiment of the present invention will be described below in detail with reference to the drawings.

1 and 2 show one embodiment of the optical deflection device. This optical deflection device includes a cylindrical storage part (not shown) and a nine-disk-shaped polyhedral part (not shown) stored in the hollow part of this storage part.
1), and a magnetic bearing part (2) that suspends this polyhedral part (1) and supports the force applied in the axial direction.

A hydrodynamic gas bearing part (3) that supports the radial force perpendicular to the axial direction of the polyhedral part (1) and the axial force;
1) at a high speed higher than the enemy rotation per minute. In the storage section above.

A window portion (not shown) is provided for allowing laser light to enter the polyhedral portion (1) and exit again. Further, the polyhedral portion (1) is made of copper, for example, and has an outer peripheral surface formed in a regular octagonal shape, for example. Furthermore, a cylindrical attachment portion (1a) is coaxially protruded from the upper end surface of the polyhedral portion (1). On the other hand, the hydrodynamic gas bearing section (3).

A tapered through hole (5) is coaxially drilled in the central axis of the polyhedral part (1) with the upper end facing the larger diameter side, and a vertically extending hole is provided in the upper base (6) that exposes a part of the storage part. and a fixed shaft (7) fitted into the through hole (5) without contact. This fixed shaft (7) is fitted into the first through hole (5) from the upper end to the lower end, and the fitted portion (7a) is formed into a truncated conical shape corresponding to the shape of the first through hole (5). There is. The gap on one side between the outer circumferential surface of the fitting portion (7a) and the inner circumferential surface of the through hole (5) is set to be several μm to several tens of μm. Further, the outer circumferential surface of the fitting portion (7a) is provided with, for example, a herringbone (herringbone) having a maximum depth of several tens of pm or less.
Dynamic pressure generating grooves (8) shaped like inpbones are carved. Furthermore, the magnetic bearing part (2) has a mounting part (1
a) a first permanent magnet (9) which is ring-encircled and magnetized in the axial direction; It consists of a magnetized second permanent magnet Ql. The first and second permanent magnets (9) and (II) have opposite polarities facing each other.

An attractive force is generated between the two to suspend the polyhedral part (1), forming a so-called attraction type magnetic thrust bearing. Tsumashi, polyhedron part (1).

It is suspended without contact by the magnetic bearing part (2). However, the one-rotation drive unit (2) is a brushless flat motor (
Brushless Flat Motor), which has a rotor Ql) embedded in the upper end surface of the polyhedral part (1) with a part exposed in an annular shape, and a part of the storage part facing the rotor housing υ. The stator QJ1 is fixed to the lower base body (la).

In the optical deflection device having the above configuration, when power is supplied to the one-rotation drive unit (1-rotation drive unit) and the polyhedral part (1) floating on the magnetic bearing part (2) is rotated, the dynamic pressure generating groove (8 )・・
・Dynamic pressure is generated. As a result, the hydrodynamic gas bearing (
3), the loads in the radial and axial directions of the polyhedral portion (1) are supported without contact. Therefore, the polyhedral part (1) is
It can rotate with high stability and precision even under high speed rotation. Incidentally, if the rotation speed of the polyhedral part (1) is 10,000 revolutions per minute and the one-rotation deflection is 1 μm or less, accurate laser beam scanning is possible.

In this way, the optical deflection device of this embodiment, like the conventional one,
Polyhedral part (1) A chair in which a rotating shaft is coaxially connected to the main body,
Rotation of the polyhedral part (1) alone becomes possible.

Therefore, high rotation accuracy can be maintained with the processing accuracy of only the polyhedral portion (1). Furthermore, it is possible to downsize the device, and it is extremely easy to assemble and adjust the device.

Next, another embodiment of the present invention will be described with reference to FIGS. 3 and 4.

The optical deflection device of this embodiment has a cylindrical housing (not shown).
, a disk-shaped polyhedral mirror A stored in the hollow part of this storage part, a magnetic bearing part (151) that suspends this polyhedron part I and supports the force applied in the axial direction, and an axis of the polyhedron #Ia It is composed of a dynamic pressure gas bearing part ae that supports the force in the direction and the force in the radial direction orthogonal to the axial direction, and a rotation drive part (Lη) that rotates the polyhedral spatula (141) at a high speed of more than 100 revolutions per minute. In the storage section above.

A window portion (not shown) is provided for allowing the laser beam to enter the polyhedral portion (13) and output it again.The polyhedral portion 1 is made of copper, for example, and has an outer peripheral surface of,
It is formed into an octagon. Furthermore, a cylindrical mounting portion α barrel is coaxially protruded from the upper end surface of the polyhedral portion Q. On the other hand, the dynamic pressure gas bearing part tte includes a blind hole (11) coaxially bored in the mounting part α of the polyhedral part I, and a blind hole (11) vertically provided in the upper base body (4) forming a part of the storage part. 11, a cylindrical fixed shaft Qυ that is fitted in a non-contact manner to the polyhedral part (14), a first opposing part Q force that is annularly and coaxially protruded from the lower end surface of the polyhedral part (14), and a part of the storage part. It consists of a second opposing part (to) protruding in an annular shape so as to face the opposing part 12 on the lower base (c).In the blind hole α field of the fixed axis C! A first dynamic pressure generating groove Q in the shape of a Herringbone is carved on the outer circumferential surface of the fitted portion to a maximum depth of several tens of am or less.

The upper end surface of the second opposing portion 1j4) has a maximum depth of several tens of μm.
Spiral-shaped second dynamic pressure generating groove C2Q with a diameter of m or less...
is engraved. Furthermore, the gap between the outer circumferential surface of the fixed shaft (21) and the inner surface of the blind hole a9 and the gap between the first opposing part 12 and the second opposing part are several μm to several tens of μm.
is set to . On the other hand, a magnetic bearing part (I9 is a first permanent magnet Q7 coaxially embedded in the bottom surface of the polyhedral part (14) and magnetized in the axial direction) and A second permanent magnet (2 marks) is fixed to the lower base (C) and magnetized in the axial direction. are facing each other.

A repulsive force is generated between the two that suspends the polyhedral mirror α, forming a so-called repulsion type magnetic thrust bearing. Therefore, the one-rotation drive unit (17) has a brush L/X7 light motor (Brush 1es
s Flat Motor), which includes a rotor (2) ring-mounted around the outer periphery of the attachment part aυ of the polyhedral part I, and a stator (2) fixed to the upper base body ct3 so as to face the rotor (2). It consists of

Therefore, in the optical deflection device having the above configuration, when power is supplied to the one-rotation drive unit (lη) and the polyhedral part α floating on the magnetic bearing part α9 is rotated, the first and second dynamic pressures are generated. Dynamic pressure is generated in the grooves (C)..., (B)...

As a result, the load in the radial direction of the polyhedral portion (14) is transferred to the support plate in a non-contact manner at the portion consisting of the fixed shaft (2υ) and the blind hole α.

On the other hand, the load in the axial direction of the polyhedral mirror α is supported in a non-contact manner at the 1'8t and second opposing portions (2LC24).

Therefore, the polyhedral portion (14) can rotate with high precision and stability even under high speed rotation. 1 In this manner, the optical deflection device of this embodiment can be rotated by only the polygon mirror (14), with the rotation axis being constant. Therefore, the processing accuracy is only for the polyhedral part (14).

Can maintain high rotation accuracy of *jG. Furthermore, it is possible to downsize the device, and it is extremely easy to assemble and adjust the device.

Note that the dynamic pressure generating grooves (8) may be formed on the inner circumferential surface of the five through holes (5). Similarly, the lower end of the fixed shaft (7).

It may be formed in a cylindrical shape instead of a truncated cone (through hole (5)
The holes will also be drilled accordingly. ). Furthermore, the first and M2
The opposing portion aa', (24) may be omitted so that the entire thrust force is borne by the magnetic bearing portion (is).

〔Effect of the invention〕

The optical deflection device of the present invention can rotate the polyhedral portion without a rotation axis. Therefore, high rotation accuracy can be maintained with the processing accuracy of only the polyhedral portion. Moreover, it can greatly contribute to miniaturization of the entire device, and assembly and adjustment are extremely easy.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of an optical deflection device according to an embodiment of the present invention;
2 is a view taken along line A-A in FIG. 1, FIG. 3 is a cross-sectional view of a main part of an optical deflection device according to another embodiment of the present invention, and FIG. 4 is a view taken along line B--A in FIG. 3. It is an arrow view along the B line. (1), α9: Polyhedral mirror, (2), α9: Magnetic bearing part. (3), αf3: Dynamic pressure gas bearing section, (4), (17):
Rotation drive unit. (Force, (2υ: Fixed axis. Agent Patent attorney Noriyuki Chika (and 1 other person) 1I21 Fig. 2

Claims (1)

[Claims] A cylindrical polyhedral mirror with a plurality of reflective surfaces formed on its outer circumferential surface, a magnetic bearing that magnetically suspends the polyhedral mirror, and a rotation drive that rotates the floating polyhedral mirror by the magnetic bearing. and a fixed shaft coaxially and loosely inserted into the polyhedral mirror, and pivotally supports the polyhedral mirror in a non-contact manner by the dynamic pressure generated between the fixed shaft and the polyhedral mirror. 1. An optical deflection device comprising: a dynamic pressure gas bearing section.